This invention relates to the lubrication of gears, particularly toothed gears. Such gears are used in many applications and to extend the life of meshing gears it is necessary to arrange for their lubrication during use.
It is, of course, well known to dispose meshing gears in a case which is filled with lubricant, either solid or liquid, which permanently bathes the gears and keeps them lubricated. However, it has long been recognised that, between meshing teeth of round gears only very small amounts of lubricant are required, and certainly much less than the amount which is usually packed into casings to ensure that the gears do receive lubrication where it is required between the meshing teeth.
It is known to provide a separate lubricating gear. In U.S. Pat. No. 3,822,607 a device for lubrication of tooth flanks is disclosed comprising a fi-eely running toothed wheel in which each tooth is provided with a plurality of radial passages each having one single outlet opening in the flank of the respective tooth and the inlet openings of said passages being successively brought in communication with a source of lubrication under pressure. Similarly, DE-C-2712065 discloses a felt rim on a gear wheel, the rim being saturated with lubricant and running against a toothed wheel adapted to receive lubricant from the felt rim. Both these methods require the provision of special gear wheels and in many circumstances, particularly, for example, in power tools, room for such additional gear wheels may not be available.
GB-A-1376617 discloses a self-lubricating gear having a circular groove around one side near its peripheral teeth, which groove is closed by a plate which, near to the teeth of the gear wheel, does not make a complete seal. Lubricant in the groove leaks out under the influence of centrifugal force and lubricates the teeth. Such an arrangement requires close tolerance parts and is not easy to assemble.